The Royal New Zealand Navy as a young seaman preceded an early career in the New Zealand Police Force. He married, there were children while he studied for his law degree. Over the ensuing years he rose to Inspector level, the last six as a Legal Adviser at Police National Headquarters. In 1981 David Bates resigned to practice in criminal law. In 1989, the Government appointed him District Inspector for Mental Health, a position he continued in conjunction with his legal practice for some years. He has since practised as a barrister-sole, specialising in criminal, traffic, youth and mental health law.